This invention deals with a method of manufacturing helical baffles which support multiple tubes in shell and tube type heat exchangers. It is a known practice to place baffles within the bundle of a shell and tube type heat exchanger in order to force the shellside fluid to flow across tubes thereby increasing the efficiency of heat exchange between tubeside fluid and shell-side fluid.
There are many types of baffle configurations. The most popular type is the plate in the form of a segmented circle. The segmental baffles are arranged so that the segmented section faces are disposed opposite to each other along a bundle of tubes at specified interval, thereby causing the shellside fluid to snake through the bundle of tubes crossing the tubes in a direction perpendicular to the axis of the tubes. The amount of cut of the segmental baffles is determined by considering the shellside fluid velocity and volumetric flow rate. The shellside fluid flows through the baffle cut area by reversing the direction 180 degrees at each baffle edge, resulting in pressure loss at every turn of flow at a baffle edge. Another shortcoming of segmental baffles is the existence of a stagnant region of flow created at each corner between the baffle and the shell, resulting in inefficient heat transfer.
Heat exchangers disclosed in Japanese Patent Application No. S48-65547 (published) and Utility Patent No. S55-73190 (published) feature helical baffle plates which can be shaped so that the fluid flows smoothly along the helical channel, resulting in substantial reduction of pressure loss and at the same time giving very high heat transfer efficiency because of the absence of stagnant region of fluid in the exchanger. This is a particularly desirable feature of heat exchangers for high viscosity oil. However, the heat exchangers, incorporating such helical baffles to form single or multiple continuous helical passages, are presently manufactured by casting the helical baffles and the center pipe together for small size exchangers or for larger size by connecting cast pieces of appropriate length of helical baffle and center piece in series. This requires extensive manufacturing facilities including casting facilities and casting dies. The cast products are also inherently thick, thus wasting substantial amounts of material. This invention is made to solve the above mentioned short comings and to offer the method of manufacturing helical baffles of any size at substantially reduced cost.